Production of a smooth



United States Patent PRODUCTION .OF A SMOOTH, UNIFORM, AIR- FREEALUMINUM STEARATE GREASE John Francis Richards and'Russell AlbertThompson, Jr., Baton Rouge, La., assignors to Esso Research andEngiueering'company, a' corporation of Delaware No Drawing. Filed Oct.27, 1958, Ser. No. 769,564 4Claims. (Cl. 252'35) This invention relatesto a new process for producing a smooth, uniform, air-free aluminumstearate grease which involves the addition of a portion of the blendingoil to a baseconcentrate grease under vacuum.

There are, at present, two main methods of making and processing analuminum stearate grease. In one the grease is packagedwhenhotandmoltenand upon cooling a gel forms. This gel is of a rubberyconsistency of sucha nature as to actually bounce back a hard articlethat might be poked at it and is distinguishable from a normal greasestructure. The disadvantage of this first technique is that the hardnessof the gelwhich forms on cooling varies with the cooling rate. Thedifiering cooling rates experienced in different size containers andeven in different parts of the same container cause the grease to varyin consistency. Even samples taken from the grease kettle have differentcooling rates and consistencies from the final packaged product. Sincecontrol samples taken from the kettle do not give the same consistencyas the same grease will eventually have in the container, it is verydifficult to adjust the grease in the kettle so as to get the desiredconsistency in the container. Also a waiting period of about 48 hours tocomplete cooling and gel formation is necessary before samples from thepackage can be tested to see if they meet consistency specifications.

The other main method of commercially producing aluminum stearate greaseallows the hot, molten grease to be run into pans, air cooled to roomtemperature, dumped back into the kettle, stirred to break the gelwithout heating and then cutback to the desired consistency with oil.The pan cooled grease is a concentrate so that anyone of severaldifferent thickness greases can be made by varying the cutbackproportions. While a uniform product can be obtained by this lattermethod, it is very time consuming, laborious and requires extreme careto prevent aerating the grease since the grease is stirred while coldand any entrapped air will not easily work out of the solid grease.

The present invention now obviates the difficulties of the twoaforementioned commerical procedures, since now the rubbery gel isbroken up as the grease is initially prepared in the kettle. In this wayno go is formed after the gerase is packaged as happens in the firstmethod and the advantage of control of final consistency which is avaluable part of the second process is retained without time consumingand excess steps.

The method of the present invention involves cooling an aluminumstearate grease concentrate under vacuum and simultaneously adding thebalance of the constituent oil as a coolant. Only one sample foradjustment need be taken after cooling to a temperature of 120 F. orless. The grease may then be packaged at 120 F. or less directly fromthe kettle. The waiting and sampling occasioned by the non-uniformproduct of the other processes are now not necessary. There is no guesswork involved in adjusting consistency since the grease is cooled and2,962,440 Patented Nov. 29, 19.60

the, gel broken before sampling, by the action of the kettle paddles.

The term aluminum stearate as used in this specification and claimsincludes not only the pure aluminum monodi-, and tri-stearates andmixtures thereof in any proportion, but also includes commercialaluminum stearates. The commercial aluminum stearates are generallymixtures of the mono-, di-, and tri-soaps. The soap itself, whilevgenerally predominately stearate, may also contain minor quantities ofthe soaps of C to C fatty acids, particularly the C and C acids. Thus, atypical hi-gel aluminum stearate will consist of about /3. of thedi-soap and about /3 of the mono-soap. This monoand di-soap will beabout 55-85% stearate, with substantial amounts of palmitate and lesseramounts of other fatty acids. A .low gel stearate or oil. type" stearatewill comprise about /3 of the mono-soap and about /3 of the di-soap. Themono and di-soaps again being mixtures of soaps of various fatty acidsas described above.

The lubricating greases of the invention will comprise about 1 to 7, butpreferably, 2.5 to 5.0 parts by weight of aluminum stearate per parts byweight of mineral lubricating oili Various other additives may also beaddedto the lubricating composition inamounts of about 2 to 4' butpreferably 2.4 to 2.5 weight percent, based on the total weight of thecomposition. Examples of such additives include: oxidation inhibitorssuch as phenyl-alphanaphthylamine; corrosion inhibitors such as sorbitanmonoleate; dyes; other grease thickeners and the like.

The technique of this invention consists of heating the soap in aportion of the oil to obtain a dispersion. Generally the soap and oil isheated to about 250 to 450 F., e.g. 280 to 350 F. in about 25 to 75,preferably 30 to 35 weight percent of the total oil for about 2 to 4hours or until the solids dissolve. The kettle is then closed and putunder a vacuum so that the absolute pressure in the kettle is about 0 to7.7 p.s.i.a. Cooling water is put through the kettle jacket and thebalance of the oil is added to the kettle without affecting the vacuum.Cooling is continued until the grease is F. or less. The batch issampled, and the consistency ascertained. Finally, after making anynecessary adjustments to the consistency, the grease is packaged at atemperature of 120 F. or less. Adding the remaining portion of the oilwhile cooling also helps shorten the cooling cycle. The vacuum preventsaeration and the action of the kettle paddles breaks up any gel as itmight form in the kettle thus resulting in a uniform product.

The invention will be further understood by the following example:

Example I (all parts by weight) 31 parts by weight of a minerallubricating oil having a viscosity of 120-130 SUS. at 210 F., 4.4 partsby weight of a commercial aluminum stearate (Plymouth- Parsons No. 551)along with 2.4 parts by weight of an additive mixture consisting of 1.0part oleic acid, 0.4 part aluminum naphthenate, and 1.0 part Paratac(polyisobutylene) were mixed together in the kettle while heating to atemperature of 250300 F2, which is sufficient to dissolve the solidstearate of the composition. The kettle was then closed and put under 6p.s.i.a. Cooling water was run through the kettle jacket. Then theremainder of the lubricating oil, or about 62.2 parts by weight wasadded through a displacement meter. The composition was then cooled to120 F. or less and sampled and tested for consistency. Further coolingto room temperature showed that no further change in consistencyoccurred. The resulting composition was an excellent looking, clear,almost transparent grease with a smooth texture. Subsequent tests showedthe grease was of uniform consistency, free of gel and air-free.

As a further illustration of my invention, Example I may be repeated,but using an aluminum soap consisting of A; aluminum monostearate andaluminum distearate and omitting the additive mixture and heating to amaximum temperature of 300 F. before cooling.

In sum, the present invention comprises a method of producing analuminum-stearate-oil composition while stirring under vacuum andcooling to a temperature of 120 F. or less. In this Way the gel whichtends to set up at a temperature of about 130 F. is broken up by themixing action, and at the same time the presence of the vacuum preventsthe entrapment of air in the grease while stirring at these lowtemperatures, i.e., about 120 F. The rate of cooling or length of timein adding the remainder of the lubricating oil does not have any efiecton the process, but rather the critical features are in cooling to atleast 120 F. while stirring under vacuum.

What is claimed is:

1. A method for producing a smooth, uniform, airiree aluminum stearategrease comprising about 1 to 7 parts by weight aluminum stearate andabout 100 parts by weight of mineral lubricating oil which comprisesforming a dispersion of said aluminum stearate in about 25 to 75 wt.percent of the total oil by heating to a temperature of about 250 to 450F., cooling said dispersion to a temperature of less than about 120 F.under an absolute pressure of about 0 to 7.7 p.s.i.a. while stirring andaddin the balance of said oil, then packaging said grease.

2. A method according to claim 1, wherein said aluminum stearate is amixture of mono-, di-, and tri-stearates.

3. A method according to claim 1, wherein said aluminum stearate is acommercial aluminum stearate, comprising about to wt. percent ofstearate with minor amounts of aluminum soaps of C14-Cz2 fatty acids.

4. A method for producing a smooth, uniform, airfree aluminum stearategrease comprising about 2.5 to 5.0 parts by weight of aluminum stearateand about parts by weight of mineral lubricating oil, which comprisesforming a dispersion of said aluminum stearate in about 30 to 35 wt.percent of the total oil by heating a mixture of said stearate in oil toabout 280 to 350 F., placing the stearate-oil mixture under a reducedpressure of 0 to 7.7 p.s.i.a., adding the balance of said oil whilestirring and cooling under said reduced pressure to a temperature lessthan F.

OTHER REFERENCES The Manufacture and Application of Lubricating Greases,Boner, Reinhold Pub. Corp., N.Y., 1954, pp. 309 and 312.

1. A METHOD FOR PRODUCING A SMOOTH, UNIFORM, AIRFREE ALUMINUM STEARATEGREASE COMPRISING ABOVE 1 TO 7 PARTS BY WEIGHT ALUMINUM STEARATE ANDABOUT 100 PARTS BY WEIGHT OF MINERAL LUBRICATING OIL WHICH COMPRISESFORMING A DISPERSION OF SAID ALUMINUM STEARATE IN ABOUT 25 TO 75 WT.PERCENT OF THE TOTAL OIL BY HEATING TO A TEMPERATURE OF ABOUT 250* TO450*F., COOLING SAID DISPERSION TO A TEMPERATURE OF LESS THAN ABOUT120*F. UNDER AN ABSOLUTE PRESSURE OF ABOUT 0 TO 7.7 P.S.I.A. WHILESTIRRING AND ADDING THE BALANCE OF SAID OIL, THEN PACKAGING SAID GREASE.